Evaluation of the enzyme manganese peroxidase in an industrial sequence for the lignin oxidation and bleaching of eucalyptus kraft pulp

Manganese peroxidase produced by the white-rot fungus Bjerkandera sp. strain BOS55 was used for lignin oxidation and bleaching of eucalyptus oxygen-delignified kraft pulp. The optimization of the enzymatic stage and its implementation into an industrial chemical bleaching sequence were performed for the purpose of defining a new bleaching sequence. Parameters related to the selection and concentration of a chelating organic acid, Mn2+, and hydrogen peroxide concentrations were optimized and applied to evaluate the implementation of an enzymatic stage into a chemical sequence composed of chelator and hydrogen peroxide or hydrogen peroxide with oxygen pressure stages. The brightness, reduction of the kappa number, and remaining manganese peroxidase activity were assessed in conventional and enzyme-based bleaching sequences. High International Organization for Standardization (ISO) brightness (83%) and parallel kappa number reduction (5.5 points) were obtained with an enzymatic stage/chelator stage/hydrogen peroxide with oxygen pressure stage sequence under the best operational conditions: 33 mu M Mn2+, oxalic acid, and 41.7 mu M H2O2 added in pulses every 5 min for the enzymatic stage and a 2-h hydrogen peroxide with oxygen pressure stage at 588.4 kPa of oxygen pressure. (C) 2008 Wiley Periodicals, Inc.